624 research outputs found
Bubbles and beads : The same problem of sphere packing ?
No full textOnes can observe that bubbles in a foam are organized and deformed according to the Plateau's laws. This phenomenon is related to a problem of surface optimization : the system minimizes its surface energy. However, in wet foams, it is different. Bubbles are spheres of different sizes with low deformations. The organization of the foam seems to be closer to a problem of sphere packing.PowderRe
Semi-parametric identification of manipulator dynamics in a time-varying environment
No full textA recent trend in robotics is aimed at the cooperation between human and robot. This has led to an increased development of collaborative robot manipulators. Typical characteristics of collaborative robots are their user-friendly and lightweight design, innovative compliant mechanics, the implementation of various safety features and advanced control capabilities. These characteristics enable humans to work alongside the manipulator or interact with it. The implementation of passive compliant components such as springs and pneumatics have a beneficial effect on the level of safety for the operator. However, the added complexity often has a negative influence on the degree to which an accurate description of the system dynamics can be derived. Furthermore, the lightweight design and increasing payload-to-weight ratio amplify the effect of exogenous alterations to the system, such as attaching an object to the end effector. The work in this thesis is aimed at obtaining an accurate description of the system dynamics for control purposes. In doing so, special attention is given to dealing with instantaneous time-varying phenomena. An online semi-parametric approach is used to produce a valid description of the inverse dynamics of the considered system. The method consists of a non-parametric part which is described using Gaussian process regression (GPR) and a parametric part for which the parameters are identified using an extended Kalman filter (EKF). In this thesis, instantaneous system changes are introduced by attaching an unknown object to the end effector of the manipulator. The EKF implementation is specifically aimed at rapidly compensating for the response induced by this object. The GPR is used to compensate for remaining modeling errors. The performance of the proposed methods is evaluated in simulation. The semi-parametric description achieves high modeling accuracy, fast adaptation to instantaneous system changes and reasonable generalization capabilities. Implementing the proposed solution in real-time applications requires additional research on the subject of online GPR.Mechanical, Maritime and Materials EngineeringDelft Center for Systems and Contro
Adapting authoritarianism: institutions and co-optation in Egypt and Syria
No full textThis PhD thesis compares Egypt and Syria’s authoritarian political systems. While the tendency in social science political research treats Egypt and Syria as similarly authoritarian, this research emphasizes differences between the two systems with special reference to institutions and co-optation. Rather than reducibly understanding Egypt and Syria as sharing similar histories, institutional arrangements, or ascribing to the oft-repeated convention that “Syria is Egypt but 10 years behind,” this thesis focuses on how events and individual histories shaped each states current institutional strengthens and weaknesses. Specifically, it explains the how varying institutional politicization or de-politicization affects each state’s capabilities for co-opting elite and non-elite individuals.
Beginning with a theoretical framework that considers the limited utility of democratization and transition theoretical approaches, the work underscores the persistence and durability of authoritarianism. Chapter two details the politicized institutional divergence between Egypt and Syria that began in the 1970s. Chapter three and four examines how institutional politicization or de-politicization affects elite and non-elite individual co-optation in Egypt and Syria. Chapter five discusses the study’s general conclusions and theoretical implications.
This thesis’s argument is that Egypt and Syria co-opt elites and non-elites differently because of the varying degrees of institutional politicization in each governance system. Rather than view one country as more politically developed than the other, this work argues that Syria’s political institutions are more politicized than their Egyptian counterparts. Syria’s political arena is, thus, described as politicized-patrimonialism. Syria’s politicized-patrimonial arena produces uneven co-optation of elites and non-elites as they are diffused through competing institutions. Conversely, the Egyptian political arena remains highly personalized as weak institutions and individuals are manipulated and molded according to the president’s ruling clique. This is referred to as personalized-patrimonialism. As a consequence, Egypt’s political establishment demonstrates more flexibility in ad hoc altering and adapting its arena depending on the emergence of crises.
This study’s theoretical implications suggest that, contrary to modernization and democratization theory’s adage that institutions lead to a political development, politicized institutions within a patrimonial order actually hinder regime adaptation because consensus is harder to achieve and maintain. It is within this context that Egypt’s de-politicized institutional framework advantages its top political elite. In this reading of Egyptian and Syrian politics, Egypt’s personalized political arena is more adaptable than Syria’s. These conclusions do not indicate that political reform is a process underway in either state
Adhesion and Co-stimulatory Molecules in the Pathogenesis of Hepatic and Intestinal Schistosomiasis Mansoni
No full textInfection of a susceptible host with the blood fluke Schistosoma mansoni results in the formation of periovular granulomas and subsequent fibrosis in the target organs. Granulomogenesis and fibrogenesis are mediated by immunological events which require cell-cell and cell-matrix interactions. In this review, the role of adhesion and co-stimulatory molecules in the genesis of the schistosomal pathology (granulomogenesis and fibrogenesis) is outlined. These molecules provide essential immunological interactions not only for the initiation of granuloma formation but also for the maintenance and modulation of the schistosomal granuloma during chronic infection. Furthermore, the role of secreted soluble adhesion molecules in the different clinical forms and in the modulation of the schistosomal granuloma is discussed. Recent new insights into the role of adhesion molecules for the induction of pathology by other developmental stages of the parasite (other than eggs) will be presented
Localisation and Communication for Autonomous Deci-Zebros: Localisation and System Integration
No full textThis document describes the Bachelor Graduation Project of the Communication and System integration group of the Zebro Localisation and Communication Module. The module has been designed for a Zebro which is a six legged robot with the purpose of working in swarm-related behaviour. To make this behaviour possible a new Localisation module for Zebro as well as a communication module has been designed with a corresponding processing unit. This thesis consists of two arts; the first part covers the development of a communication module capable of autonomous communication in an homogeneous network where no predefined routes are available, also known as a mesh network. The second part covers the integration of the communication, ranging and processing subgroups from which all the components are to be placed on a printed circuit board.Zebro ProjectElectrical Engineerin
Can somatostatin control acute bleeding from oesophageal varices in patients?[ISRCTN63456799]
No full textAbstract: Background: Management of patients with bleeding oesophageal varices comprises of mainly diagnostic endoscopy, sclerotherapy and band ligation. One of the major problems to do any of the above is the active bleeding which makes any intervention difficult. The neuropeptide hormone somatostatin administered exogenously has caused a reduction in portal hypertension and variceal bleeding in patients suffering from liver cirrhosis. We believe that the symptomatic use of somatostatin for variceal bleeding in Schistosoma mansoni infected subjects can reduce bleeding, thereby alleviating the pathology caused by schistosomiasis. Methods/design: We herein present a study protocol for establishing this neuropeptide as a potential therapeutic agent in schistosomiasis. Adolescent subjects, age range varying from 12-17 years will be selected, based on several inclusion criteria, most important being infection with Schistosoma mansoni with bleeding from oesophageal varices in the last 24 hours. One group of schistosomiasis patients will be treated with somatostatin and praziquantel, the other with propanolol and praziquantel. Survival graphs will be set up to correlate somatostatin administration with survival time. A two part questionnaire will be set up to control treatment outcomes. The pre-treatment part of the clinical questionnaire will identify inclusion criteria questions, the post-treatment part of the questionnaire will identify treatment outcomes. Discussion: We expect that the administration of somatostatin as a bolus followed by a 24 hour long infusion, will stop bleeding immediately, delay rebleeding as compared to the control study group and delay mortality in the somatostatin treated subjects
Adhesion and co-stimulatory molecules in the pathogenesis of hepatic and intestinal Schistosomiasis mansoni
No full textInfection of a susceptible host with the blood fluke Schistosoma
mansoni results in the formation of periovular granulomas and
subsequent fibrosis in the target organs. Granulomogenesis and
fibrogenesis are mediated by immunological events which require
cell-cell and cell-matrix interactions. In this review, the role of
adhesion and co-stimulatory molecules in the genesis of the
schistosomal pathology (granulomogenesis and fibrogenesis) is outlined.
These molecules provide essential immunological interactions not only
for the initiation of granuloma formation but also for the maintenance
and modulation of the schistosomal granuloma during chronic infection.
Furthermore, the role of secreted soluble adhesion molecules in the
different clinical forms and in the modulation of the schistosomal
granuloma is discussed. Recent new insights into the role of adhesion
molecules for the induction of pathology by other developmental stages
of the parasite (other than eggs) will be presented
The human prion disease hypothesis does not justify the origin of bovine spongiform encephalopathy
No full text- …
